Transient loss of femoral head Tc-99m diphosphonate uptake with prolonged maintenance of femoral head architecture.

Nine pediatric patients presented with synovitis and suspected Legg-Perthes disease, hemarthrosis, acute slipped capital femoral epiphysis, prolonged traumatic hip dislocation, or transcervical femoral fracture. All had hip scintigraphs that showed loss of Tc-99m diphosphonate uptake in the affected femoral head. Radiographic changes associated with aseptic necrosis failed to appear during the initial follow-up period of three to 14 months. Repeat scintigraphy showed complete revascularization in six cases and partial revascularization in two. Reambulation at 1.5 to eight months after presentation was accomplished without recurrence of pain in seven cases, without development of x-ray changes in 5 cases. Three children developed x-ray changes associated with avascular necrosis after reambulation, while one child had minimal x-ray changes. Some children with loss of uptake in the femoral head do not develop x-ray changes associated with aseptic necrosis.